In semiconductor manufacture, a wire bonding process is used to electrically connect metal bond pads formed on a semiconductor die to the leadfingers of a leadframe. Wire bonding devices are well known in the art. U.S. Pat. Nos. 3,894,671 issued to Kulicke Jr et al., 4,877,173 issued to Fujimoro et al., and 5,082,154 issued to Ishizuka illustrate known bonding devices.
The wire bonding process occurs during the final stages of manufacture when the semiconductor device is enclosed within a sealed package. Although a variety of different packaging systems are used in the semiconductor industry, most systems include a leadframe on which the die is mounted, leadfingers, bond wires electrically connecting the leadfingers to a metal bond pad on the die, and a sealed package enclosing the various components. Initially, numerous dies are mounted on the leadframe. The metal bond pads formed on the surface of each die are connected to the leadfingers on the leadframe using a very thin wire. The dies are then enclosed within a sealed package. A portion of the leadfingers extend out through the package for connection to an external circuit. A trim and form operation is used to separate each die package and to bend the protruding leadfingers into the proper configuration.
During the wire bonding process, a heat block heats the die and the leadframe to a temperature of about 150.degree. C. to 350.degree.. A bonding capillary tool mechanically presses the wire against a bond pad on the die and then to a bonding site on the appropriate leadfinger. The bond wire is threaded through the bonding capillary. The end of the wire is then heated by an electrical discharge or a hydrogen torch to a molten state, thus forming a ball of molten metal on the end of the bond wire. The molten ball is pressed by the bonding capillary against the heated bond pad, sometimes in combination with ultrasonic vibration, to alloy the metallic elements of the wire and the metal bond pad and thereby bond the wire to the pad. The bonding capillary tool is then moved to a bonding site on the appropriate leadfinger. The wire is pressed against the heated leadfinger to bond the wire to the leadfinger. The bond wire is then tensioned and sheared. The process is repeated for each bond pad on the die.
The present invention is directed in general to an improved wire bonding capillary and, more specifically, to an improved capillary tip. It has been discovered that by incorporating multiple angles into the face of the capillary tip, the strength of the wire bond to the leadfinger is improved.